Thesis Abstract

<p> </p><p>Utilizing Palm Oil Fuel Ash (POFA) in concrete mix is a major way of turning waste to wealth. Gravel as an aggregate is cheaper than granite. Thus, obtaining an optimum combination of these materials in achieving a maximum compressive strength in concrete will go a long way in helping the construction industry.The study was carried out to establish an optimum replacement ratio for Palm Oil Fuel Ash (POFA) blended granite-gravel of concrete. Uniform water/binder (w/b) ratio of 0.5 and mixes ratio of 124 was utilized. Thirteen runs of experiments plus control were designed using the Central Composite Response Surface method (Design Expert). Based on the analysis, the increase in granite volume led to increase in compressive strength. However, increase in POFA percentage led to decrease in compressive strength at 7, 28, 56 and 90 days curing ages. The study also observed highest compressive strength at 25% POFA replacement and lowest at 35% replacement. Also, for granite, highest and lowest compressive strength were achieved at 100% and 0% replacement respectively. However, for slump height, the higher the percentage of granite or POFA in concrete, the higher the slump height. The optimization analysis showed that, at 29.69% POFA and 98.75% Granite, compressive strength of 24.29 N/mm2 and slump height of 89.36mm were achieved. The optimum strength found is slightly higher than the maximum strength achieved (24.27N/mm2) at 90 days and also, slightly lower than the control (25.33 N/mm2).<em><br></em></p><br> <br><p></p>

Thesis Overview

<p>INTRODUCTION<br><br>1.1 Background of the study<br><br>Concrete is regarded as the primary and widely used construction ingredient around the world in which cement is the key material. However, large scale cement production contributes greenhouse gases both directly through the production of CO2 during manufacturing and also through the consumption of energy (combustion of fossil fuels). Moved by the economic and ecological concerns of cement, researchers have focused on finding a substitution of cement over the last several years. In order to address both the concerns simultaneously many attempts have been made in the past to use materials available as by product or waste. This is due to the fact that the use of by product not only eliminates the additional production cost, but also results in safety to the environment. Hence, the development and use of blended cement is growing rapidly in the construction industry mainly due to considerations of cost saving, energy saving, environmental protection and conservation of resources. &nbsp; &nbsp; A number of investigations have been carried out with Palm oil fuel ash (POFA), an agro-waste ash, as potential replacement of cement in concrete. Sata et al. (2004) found compressive strength of 81.3, 85.9, and 79.8 MPa at the age of 28 days by using improved POFA with a reduced particle size of about 10 microns in concrete as replacement of 10%, 20% and 30% of cement respectively. They also reported highest strength at 20% replacement level. Tangchirapat [2009] observed the compressive strengths of ground POFA concrete in the range of 59.5–64.3 MPa at 28 days of water curing and with 20% replacement it was as high as 70 MPa at the end of 90 days of water curing. However, the drying shrinkage and water permeability were noted to be lower than that of control concrete with improved sulphate resistance. Past researchers also depict that both ground and un-ground POFA increase the water demand and thus decrease the workability of concrete. However, ground POFA has shown a good potential for improving the hardened properties and durability of concrete due to its satisfactory micro-filling ability and pozzolanic activity.<br></p>